Ureteral stent

ABSTRACT

A ureteral stent is designed to be placed within a patient&#39;s ureter to facilitate drainage from the patient&#39;s kidneys to the bladder. An elongated portion of the stent includes a length sufficient to extend substantially within the ureter from the kidney to the bladder, and the elongated portion defines a lumen extending therethrough. A retention portion extends from one end of the elongated portion and retains the position of the ureteral stent when placed substantially within the kidney. The retention portion includes an interior space that is in communication with the lumen within the elongated portion and has at least one opening for urine drainage. A flared portion extending from the other end of the elongated portion is positioned within the patient&#39;s bladder. The flared portion curves outward and includes an elastic member that maintains the shape of the flared portion when positioned within the bladder.

CROSS-REFERENCE TO RELATED CASE

[0001] This claims priority to and the benefit of U.S. provisionalpatent application serial No. 60/207,607, filed on May 26, 2000, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] This invention relates to stents and methods of maintainingpatency of a body lumen such as the ureter using stents.

BACKGROUND INFORMATION

[0003] A ureter is a tubular passageway in a body that conveys urinefrom a kidney to a bladder. Urine is transported through the ureterunder the influence of hydrostatic pressure assisted by contractions ofmuscles located within the walls (lining) of the ureter. A urologicalcondition that some patients experience is ureteral blockage orobstruction. Some common causes of ureter blockage are the formation oftumors or abnormalities within the ureteral lining or the formation andpassage of kidney stones.

[0004] Ureteral stents are medical devices designed to extend throughthe ureter and are frequently used to bypass the ureter to facilitatedrainage from a kidney to the bladder when a ureter becomes blocked orobstructed. Generally, these stents are made from small diameter tubingof a biocompatible plastic. Ureteral stents may have multiple side holesto enhance drainage and typically include retention hooks, pigtailcurls, coils, or malecots extending from both the kidney (distal) andbladder (proximal) ends of the tubing to prevent the migration of theureteral stent after placement within the ureter.

SUMMARY OF THE INVENTION

[0005] The present invention generally relates to draining fluids fromthe kidne to the bladder of a patient with a stent. Devices and methodsaccording to the invention are typically used in the treatment ofpatients suffering from an obstructed ureter to address and relieveurinary retention while minimizing patient discomfort. It is an objectof the invention to maintain the ureter open and able to pass fluidsfrom the kidney to the bladder. It is another object of the invention tominimize patient discomfort.

[0006] In one aspect, the invention relates to a ureteral stent. Theureteral stent includes an elongated portion, a retention portionextending from one end of the elongated portion, and a flared portionextending from the other end of the elongated portion. The elongatedportion has a length sufficient to extend substantially within theureter from the kidney to the bladder and defines a lumen extendingwithin. The retention portion extends from a distal end of the elongatedportion and is configured for placement and retention within the kidney.The retention portion includes an interior space in communication withthe lumen of the elongated portion and at least one opening incommunication with the interior space for urine drainage from the kidneyto the ureteral stent. The flared portion extends from a proximal end ofthe elongated portion and is configured for placement substantiallywithin the bladder. The flared portion curves outward while extendingfrom the elongated portion and includes an elastic member formaintaining the shape of the flared portion in an expanded shape whenlocated within the bladder. The flared portion is collapsible to allowentry of the flared portion into the bladder through the urethra.

[0007] Embodiments of this aspect of the invention can include thefollowing features. For example, the elastic member of the flaredportion may be made from a shape-memory material or a superelasticmaterial, such as for example, a nickel-titanium alloy, or anelastomeric material. In some embodiments, the elastic member is a ringor loop of material that is embedded within or attached to the flaredportion. The shape of the ring or loop may be round, oval, or evenelliptical, or it may even be patterned to have a sinusoidal orsaw-tooth shape. In other embodiments, the elastic member may include aplurality of collapsible spokes. These collapsible spokes have a firstand a second end. The first end of the spokes is attached to a wall ofthe flared portion and the second end is attached to a hub. In anexpanded state, the spokes extend radially from the hub. In a collapsedstate, the spokes extend longitudinally from the hub.

[0008] In some embodiments, the flared portion may further include avalve that allows fluid to pass from the elongated portion through thevalve, out of the flared portion, and into the bladder, but not from thebladder back into the elongated portion. The flared portion itself ismade from a thin flexible material and may be corrugated. The retentionportion, which is located within the kidney when the ureteral stent isplaced within the patient, may be made from a shape-memory or asuperelastic material and may have a coil or other retention structureshape. In other embodiments, the entire ureteral stent including theelongated portion, the retention portion, and the flared portion issized to fit within a cystoscope.

[0009] In general, in another aspect, the invention features a method ofinserting within a urinary tract a ureteral stent such as the stentdescribed above. The method includes inserting the stent into theurinary tract of a patient and positioning the ureteral stent within theureter of the patient such that the retention portion is within thekidney and the flared portion is within the bladder. The method may alsoinclude collapsing the flared portion of the ureteral stent prior toinsertion and allowing the flared portion to expand within the bladder.The method may further include providing a cystoscope sized to receivethe ureteral stent and using the cystoscope to insert and position theureteral stent within the urinary tract of the patient.

[0010] The foregoing and other objects, aspects, features, andadvantages of the invention will become more apparent from the followingdescription and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the drawings, like reference characters generally refer to thesame parts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention.

[0012]FIG. 1 is a schematic view of a human urinary tract.

[0013]FIG. 2A is a schematic view of an embodiment of a ureteral stentaccording to the invention positioned within the human urinary tract.

[0014]FIG. 2B is a front view of the ureteral stent of FIG. 2A.

[0015]FIG. 2C is an enlarged front view of one embodiment of a flaredportion of the ureteral stent of FIG. 2A in an expanded configuration.

[0016]FIG. 2D is a front view of one embodiment of an elastic member.

[0017]FIG. 2E is an enlarged cross-sectional view of a portion of theureteral stent of FIG. 2A showing one embodiment of a transition betweenan elongated portion and the flared portion.

[0018]FIG. 2F is another enlarged cross-sectional view of a portion ofthe ureteral stent of FIG. 2A showing another embodiment of a transitionbetween an elongated portion and the flared portion

[0019]FIG. 3A is an enlarged front view of another embodiment of aflared portion in an expanded configuration.

[0020]FIG. 3B is an enlarged front view of the flared portion of FIG. 3Ain an insertion/collapsed configuration.

[0021]FIG. 4A is an enlarged front view of another embodiment of aflared portion in an expanded configuration.

[0022]FIG. 4B is an enlarged front view of the flared portion of FIG. 4Ain an insertion/collapsed configuration.

[0023]FIG. 5A is an enlarged front view of another embodiment of aflared portion in an expanded configuration.

[0024]FIG. 5B is an enlarged front view of another embodiment of aflared portion in an expanded configuration.

[0025]FIG. 6A is an enlarged front view of another embodiment of aflared portion in an expanded configuration.

[0026]FIG. 6B is an enlarged side view of the flared portion of FIG. 6Aalso in an expanded configuration.

[0027]FIG. 6C is an enlarged view of a reinforcing member of the flaredportion shown in FIGS. 6A and 6B.

[0028]FIG. 6D is an enlarged front view of the flared portion of FIG. 6Ain an insertion or collapsed configuration.

[0029]FIG. 7 is a front view of a mold used to form the flared portionof FIG. 2C.

DESCRIPTION

[0030] Referring to FIG. 1, in a human urinary tract 100, the ureters110 transport urine from the kidneys 105 to the bladder 120. When one orboth of the ureters 110 become blocked or obstructed due to, forexample, the growth of a tumor or the entrapment of a kidney stone, atemporary alternative path is needed to provide fluid drainage. Ureteralstents are medical devices that are implanted within the ureters 110 torestore their patency and fluid drainage. Conventional ureteral stentshave pigtail or hook ends designed to retain the stent within theureter. In the bladder, these retention structures contact the bladderlining within a sensitiye area known as the trigone. The trigone 130 isa triangular section of the bladder 120 located between the urethralopening 125 and the two ureteral orifices 115. It is a sensitive regionof the bladder that contains a nerve bed. Typically, foreign objectswithin the trigone rubbing against the bladder may stimulate this nervebed causing the patient to experience urinary urgency sensations.Stimuli within the trigone are due to contact with the bladder endportion of these conventional stents and are believed to be the sourceof patient discomfort.

[0031] This invention generally concerns ureteral stents that, whenpositioned within the ureter of a patient, significantly reducediscomfort to the patient. The structure of ureteral stents according tothe invention provides an increase in comfort for a patient, because theproximal or bladder portion of the ureteral stent is designed tominimize stimulation in the trigone.

[0032] To minimize stimulation of the nerves within the trigone,according to the invention, a portion of the stent that resides in thebladder has a horn shape design that flares or curves outward and istherefore referred to as a flared portion. The shape of the flaredportion provides the ureteral stent of the present invention with broad,soft surfaces, which softly contact the end of the ureter where itenters the trigone. In ideal position, the shape will contact only thisarea and not contact other area of the trigone or of the bladdersurface. The shape of the flared portion may be symmetrical along alongitudinal axis of the ureteral stent, as shown, for example, in FIG.5A. Alternatively, the flared portion may be shaped such that a medianaxis of the flared portion is tilted with respect to the longitudinalaxis of the stent, as shown, for example in FIG. 5B. The flared portionincludes a wall that forms the horn shape. This wall may be smooth orcorrugated. The wall includes a rim that defines the largest opening tothe flared portion. To act as a retention structure, the rim, whenexpanded, has a size that is larger than the ureteral orifice.Generally, a normal ureter has a diameter size that may extend up tobetween about 2 millimeters and 6 millimeters. After dilation of theureter, the ureter's diameter size may be further increased up to about8 millimeters. Therefore the expanded diameter size of the rim should be8 millimeters or larger to prevent the flared portion from migratinginto the ureter and preferably, the diameter of the rim is sized in therange between about 9 millimeters to 12 millimeters. The rim may besmooth, or have a pattern according to the invention that is undulatingor jagged. The rim may be symmetrical and have a generally overallround, oval, or elliptical shape. Alternatively, the rim may also beasymmetrical. The flared portion further decreases nerve stimulationwithin the trigone by providing only a small amount of material withinthe bladder. The flared portion is made from a thin flexible materialthat allows the flared portion to achieve a high surface area to contactpressure ratio as well as to contour and tilt naturally to conform tothe shape of the ureteral orifice.

[0033] To reinforce the thin wall and maintain the shape of the flaredportion expanded within the bladder, the flared portion further includesan elastic member. The elastic member may be embedded with the wall ofthe flared portion or attached to the rim such that, when the elasticportion is extended, the form of the flared portion resembles a trumpetor a horn.

[0034] Both the elastic member and the flared portion are collapsible toallow for insertion through the urethra to the bladder. Once locatedwithin the bladder, the elastic member springs back to its original andexpanded state to reform and support the shape of the flared portion.

[0035] Suitable elastic members may take a variety of forms and shapesand a variety of positions within the flared portion. For example, theelastic member of the flared portion may be a loop of an elastic andresilient material. The loop may have a sinusoidal or saw-tooth wavepattern. Alternatively, the elastic member may include a center hubconnected to collapsible spokes similar to the mechanism within anumbrella with the spokes attached at least to or near the rim of thehorn.

[0036] Suitable material for the elastic member includes, but is notlimited to rubbers, shape-memory alloys and superelastic materials. Bothsuperelastic and memory-shape materials are well known materials thatmake it possible for a segment or portion to have a particular firstshape that can be reversibly modified to a second shape. For example, itis possible to configure a segment of a superelastic material into aclosed loop and then with the aid of a sheath collapse the looptemporarily during insertion and placement within a patient's body. Uponremoving the sheath, the loop returns to the original radially expandedshape. A shape-memory material can also alternate between the firstshape and the second shape. However, shape-memory materials rely onphase changes triggered by changes in temperature to produce the shapechange. Generally, nickel-titanium alloys having a nickel compositionwithin the range of about 50 to 53% transition from an elastic phase toa plastic phase at about normal human body temperature and are oftenused for various medical devices. Nickel-titanium alloys having a nickelcomposition greater than 53% may also be used to form elastic members orretention devices, if a heat source is provided to treat the material invivo to produce the desired phase change.

[0037] The material that forms the thin flexible wall of the flaredportion may be selected from any biocompatible polymer or plastic, suchas, for example silicone or other PTFE polymers. The shape of the flaredportion may be manufactured by dip molding, machining, thermosetting, orvacuforming. These along with other features of ureteral stents of theinvention are described in further detail below.

[0038] Now referring to FIG. 2A, a ureteral stent 200 of the inventionis located within the human urinary tract 100. The ureteral stent 200includes an elongated portion 205 that spans between a retention portion220 and a flared portion 230. The elongated, retention, and flaredportions 205, 220, 230 are indicated generally in FIG. 2B. The elongatedportion 205 extends substantially the entire length of one of theureters 110 when placed within the urinary tract 100 of a patient andhas a distal end 215 and a proximal end 225. Within the elongatedportion 205, extending between the distal end 215 and the proximal end225 is a passageway or a lumen for transporting bodily fluids, such as,for example, urine. Located along the length of the ureteral stent 200,as shown in FIG. 2A, can be a plurality of openings 207 in communicationwith the lumen. These openings 207 are optional, and if present tend toincrease drainage of urine through the stent and into the bladder 120.

[0039] The retention and flared portions 220, 230 extend from therespective distal and proximal ends 215, 225 of the elongated portion205 and have shapes designed to retain the ureteral stent 200 within theureter 110 and thereby prevent migration of the ureteral stent 200. Inthe embodiment disclosed in FIG. 2A, the distal retention portion 220 isa pigtail coil that extends from the distal end 215 of the elongatedportion 205. The retention portion 220 can be straightened to allowpassage of the retention and elongated portions 220, 205 all the waythrough the ureter 110. Once the retention portion 220 is positionedwithin the kidney 105, the retention portion 220 is allowed to re-coilto anchor the ureteral stent 200 within the kidney 105, therebypreventing proximal migration of the stent and keeping the flaredportion snug against the ureteral orifice. In some embodiments, theretention portion may be able to coil a self-adjustable number of turnsto eliminate any excessive length of the elongated portion, therebyallowing the flared portion to remain snug against the ureteral orificeand permitting the stent to fit a greater range of ureter length.Alternatively, the distal retention portion may also be a hook, amalecot, or other structure that functions as an anchor to retain theureteral stent 200 within the kidney 105. Within the retention portion220, there is an interior space (an extension of the lumen of theelongated portion 205, in the disclosed embodiment) that is incommunication with the lumen of the elongated portion 205. At least oneopening 212 in communication with the interior space is present on theretention portion 220, such that urine or any other bodily fluid fromthe kidney 105 may enter this opening 212. After entering into theopening 212, fluid is carried through the interior space, down into thelumen of the elongated member 205.

[0040] The flared portion 230 extends and curves outward from theproximal end 225 of the elongated portion 205. The flared portion 230 isa floppy, horn-shaped structure that is designed not only to retain oranchor the proximal end 225 of the elongated portion 205 within thebladder 120, but also to minimize stimulation in the sensitive trigone130. The horn shape of the flared portion 230 has soft, convex surfacesthat coritact areas only around the ureteral orifice 115. The flaredportion 230 has an overall larger diameter than the ureter 110 andprevents the stent 200 from migrating or travelling into the ureter 110.The ureteral stent 200 achieves comfort for the patient by permittingonly soft, flexible surfaces with a high surface area to contactpressure ratio to come in contact to sensitive bladder mucosal tissue,while achieving a desirable small total contact surface area in thebladder 120. The flared portion 230 contacts the bladder 120 only in thearea near the ureteral orifice 115, and not elsewhere within the trigone130. Pressure on the bladder from contact with the flared portion 230 isdistributed over a larger surface area compared to traditional proximalretention devices, such as, for example, a pigtail coil and is thusgentler and less irritating to the patient.

[0041] Referring to FIGS. 2B and 2C, the flared portion 230 has a smoothwall 250 defining the flared, horn shape and an elastic member 240 thatis either embedded within or attached to the wall 250 near its rim 255.The wall 250 is made from a flexible, biocompatible material, such as,for example, silicone and has a substantially thin wall thickness, suchthat the wall 250 is floppy and easily compressible. In FIGS. 2A-2C, theelastic member 240 has an undulating (sinusoidal) annular shape and isdisposed near the rim 255. The elastic member 240 may be embedded withinthe wall 250 of the flared portion 230, as shown in FIG. 2C.Alternatively, in other embodiments, the elastic member may be glued ormechanically fastened to either the inside or outside of the wall 250.The elastic member 240 is shown by itself in FIG. 2D and may be madefrom an elastomer, such as, for example, rubber or other polybutadienylmaterial, or from a shape-memory alloy, such as, for example, anickel-titanium alloy. The elastic member 240 may be expanded andcollapsed and is biased towards an expanded state. The elastic member240 will return to the expanded state in the absence of external forcesacting upon it. In the expanded state, the elastic member 240 supportsand maintains the flared, horn shape of the wall 250. In the collapsedstate, the elastic member 240 has a perimeter substantially equivalentto a perimeter of the elongated portion 205 to facilitate insertionthrough the urethra.

[0042] In some ureteral stents, a back-flow of urine can occur duringvoiding and generally results in patient discomfort. To increase patientcomfort, the flared portion 230 may also include a valve 260 to preventurine from traveling up the ureter 110 from the bladder to the kidneys.In the disclosed embodiment, the valve 260 is a flap of flexiblematerial that extends within the flared portion 230 across the lumen ofthe elongated portion 205. The valve 260 is located near the proximalend 225 of the elongated portion 205 and is sized such that in theabsence of fluid flowing down from the lumen of the elongated portion205 the flap substantially blocks the distal end 225. Thus, as long asurine is flowing antegrade under the influence of normal hydrostaticpressure, the valve will remain open and will allow the urine to passfrom the kidney to the bladder. However, urine already located withinthe bladder substantially can not re-enter the kidney because the valve260 blocks the lumen in distal end 225 of the elongated portion 205,thereby preventing urine from travelling up the ureteral stent 200 ifthe pressure relationships are reversed preventing retrograde flow.

[0043] Because of its thin wall, the flared portion 230 has a lessamount of material (compared to a structure with a greater wallthickness) with which to stimulate the nerves within the trigone. Theremainder of the stent (i.e., the elongated portion and the retainingportion) may be made of thicker material to provide stability andstructural integrity such that it resists buckling and kinking. Theelongated portion 205 requires a certain amount of stiffness to maintainpatency through an obstructed ureter. The wall thickness transitionsfrom a thin wall in the flared portion 230 to a thicker wall in theelongated portion 205 in a transition zone 233. This transition can beaccomplished by increasing the wall thickness in the transition zone 233from the flared portion 230 through the distal end 225 of the elongatedportion 205, by using a different material to form the elongated portionthat has a greater durometer than the flared portion, or by acombination of both.

[0044]FIGS. 2E and 2F show cross-sectional views of the transition zone233 between the flared portion 230 and the elongated portion 205. Inthese two figures, the transition in stiffness is accomplished byincreasing the wall thickness and providing two different materials forthe flared portion 230 and the elongated portion 205. The materialselected for the elongated portion 205 should have a greater durometerthan the material selected for the flared portion 230, thereby providingthe elongated portion 205 with a greater stiffness to maintain patencythrough an obstructed ureter. Within the transition zone 233, thestiffness gradually increases due to the dovetailing of tapered proximalend portion 234 of the elongated portion 205 and tapered distal endportion 235 of the flared portion 230. In FIG. 2E, the inner wall of theflared portion tapers from an inner diameter the size of the lumen tothe outer diameter of the elongated portion. In FIG. 2F, the outer wallof the flared portion tapers from the outer diameter of the elongatedportion to the inner diameter of the lumen. In both embodiments, apusher landing area 236 is created at the proximal end of theirjunction. When the elongated portion 205 and the flared portion 230 areformed from different materials, as shown in FIGS. 2E and 2F, theelongated and flared portions 205, 230 may be joined either by a gluing,molding, or mechanically fastening the two portions together. If amechanical fastener is used, it may be embedded within the walls of theelongated and flared portion so as not to directly contact the ureter orthe bladder or obstruct the lumen.

[0045] The flared portion 230, in FIGS. 2A-2F, has a sinusoidal loopedelastic member 240 embedded within the wall 250 that maintains the shapeof the flared portion 230 when the elastic member 240 is in the expandedstate. The sinusoidal pattern of the elastic member 240 undulates alongthe wall 250 of the flared portion 230 between a proximal transverseplane A and a distal transverse plane B as shown in FIG. 2E. Whenexpanded, the elastic member 240 maintains the flared horn shape of thewall 250 wide open. When collapsed, the perimeter of the elastic member240 is sized to permit insertion and travel through the human urinarytract 100. Because the elastic member 240 is either embedded or attachedto the wall 250 of the flared portion 230, when the elastic member 240is collapsed, the flared portion 230 and the wall 250 are collapsed aswell. As the flared portion 230 collapses, the wall 250 folds toaccommodate the size of the collapsed elastic member 240. The sinusoidalshape of the looped elastic member 240 prevents excess pre-folding ofthe wall 250 and is desirable because folding can lead to deformation orcrimping of the wall 250 over itself. In FIGS. 2A-2F, the wall 250 ofthe flared portion is smooth. In some embodiments, the wall of theflared portion may be corrugated as shown in FIGS. 3A and 3B to furtheraid in the collapse of a flared portion. FIG. 3A shows a flared portion330 having a sinusoidal looped elastic member 340 in the expanded stateembedded within a wall 350 near the rim 355 made of a corrugated,flexible material. Alternatively, the pattern of the elastic member neednot be sinusoidal to limit the amount of folding needed to collapse thewall of the flared portion, as any other waving pattern would providesufficient yield to radial constriction. In other embodiments, anelastic member 440 may have, for example, a saw-tooth pattern as shownin FIGS. 4A and 4B.

[0046] In some embodiments of the present invention, the elastic membermay be a smooth planar loop and is collapsed radially and foldedlongitudinally for ease of insertion. Referring to FIGS. 5A and 5B, anelastic member 540 of a flared portion 530 has a curvilinear shape andembedded within the wall 550 near the rim 555. The elastic member 540forms a loop that includes more than one focal point of curvature, suchas, for example, an ellipse or an oval. The elastic member 540 may beexpanded or collapsed, and is biased towards an expanded state. Theplane of the loop (elastic member 555) forms an angle α of 90 or lessdegrees with a longitudinal axis L of the elongated portion 205. Toprevent longitudinal folding of the wall 550 while the elastic element540 is collapsed and folded over the length of the flared portion, theflared portion 530 may be tilted such that a median axis M of the flaredportion 530 forms an angle β with the longitudinal axis L of theelongated portion 205 as shown in FIG. 5B.

[0047] Referring to FIGS. 6A-6D, alternatively, a wall 650 of flaredportion 630 may be maintained in an expanded state with a plurality ofspokes 640. The spokes 640 have a first end 641 and a second end 642.The first end 641 of the spokes 640 is attached to the wall 650. Thesecond end 642 is attached to a center hub 645. The spokes 640 arecollapsible and expandable and may be made from a shape-memory alloy ora superelastic material, such as, for example, a nickel-titanium alloy.When the spokes 640 are expanded, the spokes 640 extend radially outfrom the hub 645 and thus support the flared, horn shape of the wall650. When the spokes 640 are collapsed, as in FIG. 6D, the spokes 640extend longitudinally from the hub 645 and the wall 650 folds toaccommodate the collapsed spokes 640.

[0048] All of the flared portions described above provide comfort to apatient because they are all designed to minimize stimulation within thetrigone of the bladder. The flared portions of the present invention,while so designed are simultaneously designed to anchor the ureteralstent within the bladder so as to prevent migration of the stent up theureter towards the kidney. Ureteral stents, devices that maintainpatency from the kidneys to the bladder that include the flared portionsas described herein will provide patients with increased comfort.

[0049] Various techniques, such as, for example, machining, injectionmolding, dip molding, and thermosetting may be used to manufacture theflared portion of the present invention. To machine a flared portion, amaterial such as, for example, a hydrophilic monomer that changes itsmechanical characteristics from rigid to elastic with hydration may beutilized to produce the wall of the flared portion. Once dehydrated,hydrophilic materials may be easily machined because they are rigidsolids. After machining, the flared portion may be re-hydrated producinga flared portion that is soft and pliable. An elastic member such as aring or a plurality of collapsible spokes supported by a central hub maythen be glued or mechanically attached to the wall of the flaredportion. Alternatively, a material that changes its mechanicalcharacteristics with temperature instead of hydration may also be usedto machine the flared portion.

[0050] A manufacturer may also use standard injection molding techniquesto create the flared portion. When the injection molding technique isutilized, the manufacturer places the elastic member within the moldnear where the rim will be formed prior to injecting the material thatforms the wall of the flared portion. When the wall material isinjected, the elastic member becomes embedded within the rim.

[0051] Alternatively, a dip molding technique may be used to manufacturethe flared portion. Referring to FIG. 7, a manufacturer dips a solidmold 700 into a bath of liquid polymer such as, for example, liquidsilicone. Once the manufacturer removes the mold from the bath, theliquid polymer solidifies around the solid mold 700. A valve thatcontrols the directional flow of urine may easily be produced within theflared portion using this technique, if a slit 710 is cut within thesolid mold 700. The manufacturer may loosely attach an elastic membersuch as a loop of an elastic material or a plurality of spokes to themold such that the elastic member becomes embedded within the flaredportion during manufacturing.

[0052] In operation, the retaining portion of the ureteral stent isinserted through the urethra and advanced through the bladder and ureterand placed within the kidney. Prior to insertion, the retaining portion,if a coil is temporarily straightened and the flared portion istemporarily collapsed for insertion into the patient's body.

[0053] The coil may be straightened over a guidewire, which slideswithin the lumen of the ureteral stent and is sufficiently stiff to holdthe curl in a straight configuration when placed within the ureteralstent. Alternatively, if other retention devices other than a coil areused as the retaining portion, they are placed in an insertionconfiguration, for example, hooks are straightened and malecots arecollapsed. Prior to insertion into the body, the flared portion may becollapsed by placement of the entire ureteral stent within a cystoscopeor a sheath. The inner diameter of the cystoscope should besubstantially similar to the outer diameter of the elongated member, andthus when the ureteral stent is placed within the cystoscope or sheath,the flared portion would be in a collapsed configuration.

[0054] To position the ureteral stent within the urinary tract of apatient, a medical professional, such as a physician inserts theguidewire into the patient's urethra and advances the guidewire until adistal end of the guidewire is within the kidney. Once the guidewire isproperly placed with its distal end within the kidney and its proximalend external to the body of the patient, the physician slides thecystoscope or sheath over the guidewire. Then the physician slides aureteral stent in accordance with the present invention over theproximal end of the guidewire such that the guidewire, the cystoscope,and the ureteral stent all have the same central axis and that ureteralstent is radially positioned between the cystoscope and the guidewire.The physician may use a pusher to advance the ureteral stent through theurinary tract until the proximal end of the elongated portion is locatedwithin the kidney. At this point, the flared portion should be withinthe bladder because the length of the elongated portion is substantiallyequivalent to the length of the ureter, which connects the kidney to thebladder. Once the retaining portion is positioned within the kidney andthe flared portion is within the bladder, the cystoscope and theguidewire are withdrawn, thereby allowing the retaining portion tore-coil and the flared portion to expand.

[0055] Variations, modifications, and other implementations of what isdescribed herein will occur to those of ordinary skill in the artwithout departing from the spirit and the scope of the invention. Theinvention is not to be limited only to the preceding illustrativedescription.

What is claimed is: 1-20. (Cancelled)
 21. A ureteral stent, comprising:an elongated portion defining a lumen and including a length; aretention portion extending from one end of the elongated portion,defining an interior space in communication with the lumen; a flaredportion curving outward while extending from the other end of theelongated portion, the flared portion being collapsible into a collapsedstate, the flared portion comprising an elastic member maintaining theshape of the flared portion in an expanded state, the elastic memberhaving a plurality of collapsible spokes, said spokes being attached ata first end to the flared portion and at a second end to a hub, saidspokes extending radially from said hub in the expanded state andextending longitudinally from said hub in the collapsed state.
 22. Theureteral stent of claim 21, wherein said hub is substantially circularin shape.
 23. The ureteral stent of claim 21, wherein said spokes aresubstantially linear.
 24. The ureteral stent of claim 21, wherein saidspokes are made of at least one of a shape-memory alloy and asuperelastic material.
 25. A ureteral stent, comprising: an elongatedmember having a side wall that defines a lumen, the elongated memberincluding a distal end portion and a proximal end portion, the distalend portion including a retention member, the proximal end portionincluding a flared portion, the flared portion including a hub, a firstspoke, and a second spoke, the first spoke having a first end portioncoupled to the side wall and a second end portion coupled to the hub,the second spoke having a first end portion coupled to the side wall anda second end portion coupled to the hub.
 26. The ureteral stent of claim25, wherein the first spoke and the second spoke extend radially fromthe hub.
 27. The ureteral stent of claim 25, wherein the flared portionhas an expanded configuration and a collapsed configuration, the firstspoke and the second spoke extend radially from the hub when the flaredportion is in the expanded configuration, the first spoke and the secondspoke extend longitudinally from the hub when the flared portion is inthe collapsed configuration.
 28. The ureteral stent of claim 27, whereinthe first spoke and the second spoke are disposed within a plane in saidexpanded configuration.
 29. The ureteral stent of claim 25, furthercomprising: a third spoke having a first end portion coupled to the sidewall and a second end portion coupled to the hub.
 30. The ureteral stentof claim 25, wherein the flared portion has an expanded configurationand a collapsed configuration, the lumen is configured to convey urinein a direction from the kidney to the bladder, the first spoke extendsin a direction substantially orthogonal to the direction of theconveyance of urine when the flared portion is in the expandedconfiguration, the first spoke extends in a direction substantiallyparallel to the direction of the conveyance of urine when the flaredportion is in the collapsed configuration.
 31. The ureteral stent ofclaim 25, wherein the hub is substantially circular in shape.
 32. Theureteral stent of claim 25, wherein the first spoke is substantiallylinear.
 33. The ureteral stent of claim 25, wherein the first spoke ismade of at least one of a shape-memory alloy and a superelasticmaterial.
 34. The ureteral stent of claim 25, wherein the hub, the firstspoke, and the second spoke are configured to retain the flared portionin its expanded configuration when the flared portion is located withinthe bladder of the patient.
 35. A method of disposing at least a portionof a ureteral stent within a bladder of a patient, the ureteral stenthaving an elongate portion and a flared portion, the flared portionincluding a hub, a first spoke, and a second spoke, the first spokeincluding a first end portion coupled to the hub and a second endportion coupled to the elongate portion, the second spoke including afirst end portion coupled to the hub and a second end portion coupled tothe elongate portion, comprising: positioning the first spoke and thesecond spoke such that the first spoke and the second spoke generallyextend longitudinally and the second end portion of the first spoke isdisposed a first distance from the second end portion of the secondspoke; inserting at least a portion of the ureteral stent into thebladder of the patient; and repositioning the first spoke and the secondspoke such that the second end portion of the first spoke is disposed asecond distance from the second end portion of the second spoke, thefirst distance being smaller than the second distance.
 36. The method ofclaim 35, wherein the positioning the first spoke and the second spokeincludes moving the hub from a position proximate a bladder end portionof the ureteral stent in a direction towards a kidney end portion of theureteral stent.
 37. The method of claim 35, further comprising:inserting at least a portion of the ureteral stent into a kidney of thepatient.